1. Field of the Invention
The present invention relates to a subscriber line module for connecting a plurality of subscriber terminals to an integrated services digital network (ISDN).
2. Description of the Prior Art
In the ISDN, the so-called network termination NT is defined, which terminates the transmission link to the subscriber terminal exchange via the likewise defined U.sub.0 interface on the network side and contains an internationally standardized user/network interface S.sub.0 on the subscriber side, which allows the direct connection of digital (ISDN) terminals to the network.
To allow the connection of analog terminals, which are designed to be connected only to an analog telephone network, a terminal adapter TA is necessary between the terminal and the S.sub.O interface ("ISDN-Praxis" K. H. Rosenbrock, G. Hentschel, Loseblatt-Ausgabe, ISBN-3-923759-10-X (Grundwerk 1988), Chapters 3.2 and 5.4).
Particularly if existing analog terminals are to be used in the ISDN, this terminal adapter TA represents a very expensive solution.
The technical problem to be solved by the invention is to implement a universal subscriber line module which makes it possible to connect arbitrary analog and digital terminals to an integrated services digital network (ISDN) at low cost.